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authorYing Han <yinghan@google.com>2010-10-26 14:21:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-26 16:52:05 -0700
commit3d5992d2ac7dc09aed8ab537cba074589f0f0a52 (patch)
tree0fbb51026e8aa13ddd7a6516c04471ceb97bc277 /fs
parent0f4d208f1975f16f269134cee5f44c1f048581da (diff)
oom: add per-mm oom disable count
It's pointless to kill a task if another thread sharing its mm cannot be killed to allow future memory freeing. A subsequent patch will prevent kills in such cases, but first it's necessary to have a way to flag a task that shares memory with an OOM_DISABLE task that doesn't incur an additional tasklist scan, which would make select_bad_process() an O(n^2) function. This patch adds an atomic counter to struct mm_struct that follows how many threads attached to it have an oom_score_adj of OOM_SCORE_ADJ_MIN. They cannot be killed by the kernel, so their memory cannot be freed in oom conditions. This only requires task_lock() on the task that we're operating on, it does not require mm->mmap_sem since task_lock() pins the mm and the operation is atomic. [rientjes@google.com: changelog and sys_unshare() code] [rientjes@google.com: protect oom_disable_count with task_lock in fork] [rientjes@google.com: use old_mm for oom_disable_count in exec] Signed-off-by: Ying Han <yinghan@google.com> Signed-off-by: David Rientjes <rientjes@google.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/exec.c5
-rw-r--r--fs/proc/base.c30
2 files changed, 35 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index 6d2b6f936858..3aa75b8888a1 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -54,6 +54,7 @@
#include <linux/fsnotify.h>
#include <linux/fs_struct.h>
#include <linux/pipe_fs_i.h>
+#include <linux/oom.h>
#include <asm/uaccess.h>
#include <asm/mmu_context.h>
@@ -759,6 +760,10 @@ static int exec_mmap(struct mm_struct *mm)
tsk->mm = mm;
tsk->active_mm = mm;
activate_mm(active_mm, mm);
+ if (old_mm && tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
+ atomic_dec(&old_mm->oom_disable_count);
+ atomic_inc(&tsk->mm->oom_disable_count);
+ }
task_unlock(tsk);
arch_pick_mmap_layout(mm);
if (old_mm) {
diff --git a/fs/proc/base.c b/fs/proc/base.c
index dc5d5f51f3fe..6e50c8e65513 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1047,6 +1047,21 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
return -EACCES;
}
+ task_lock(task);
+ if (!task->mm) {
+ task_unlock(task);
+ unlock_task_sighand(task, &flags);
+ put_task_struct(task);
+ return -EINVAL;
+ }
+
+ if (oom_adjust != task->signal->oom_adj) {
+ if (oom_adjust == OOM_DISABLE)
+ atomic_inc(&task->mm->oom_disable_count);
+ if (task->signal->oom_adj == OOM_DISABLE)
+ atomic_dec(&task->mm->oom_disable_count);
+ }
+
/*
* Warn that /proc/pid/oom_adj is deprecated, see
* Documentation/feature-removal-schedule.txt.
@@ -1065,6 +1080,7 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
else
task->signal->oom_score_adj = (oom_adjust * OOM_SCORE_ADJ_MAX) /
-OOM_DISABLE;
+ task_unlock(task);
unlock_task_sighand(task, &flags);
put_task_struct(task);
@@ -1133,6 +1149,19 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
return -EACCES;
}
+ task_lock(task);
+ if (!task->mm) {
+ task_unlock(task);
+ unlock_task_sighand(task, &flags);
+ put_task_struct(task);
+ return -EINVAL;
+ }
+ if (oom_score_adj != task->signal->oom_score_adj) {
+ if (oom_score_adj == OOM_SCORE_ADJ_MIN)
+ atomic_inc(&task->mm->oom_disable_count);
+ if (task->signal->oom_score_adj == OOM_SCORE_ADJ_MIN)
+ atomic_dec(&task->mm->oom_disable_count);
+ }
task->signal->oom_score_adj = oom_score_adj;
/*
* Scale /proc/pid/oom_adj appropriately ensuring that OOM_DISABLE is
@@ -1143,6 +1172,7 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
else
task->signal->oom_adj = (oom_score_adj * OOM_ADJUST_MAX) /
OOM_SCORE_ADJ_MAX;
+ task_unlock(task);
unlock_task_sighand(task, &flags);
put_task_struct(task);
return count;

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